Plasma processing apparatus

ABSTRACT

According to one embodiment, a plasma processing apparatus that includes a process target holding portion and a plasma generating unit in a chamber, and processes a process target by using generated plasma is provided. An yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber on a generation region side of the plasma. The yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more and 200 μm or less, has a film density of 90% or more, and is such that yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in area ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2011-40190, filed on Feb. 25, 2011; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a plasma processingapparatus.

BACKGROUND

Conventionally, in a micro-patterning process in manufacturingsemiconductor devices, liquid crystal display devices, and the like, anRIE (Reactive Ion Etching) apparatus is used. In the RIE apparatus,etching is performed by setting the inside of a chamber in alow-pressure state and turning fluorine based gas or chlorine based gasintroduced into the chamber into plasma. The inner wall and the internalstructural members of such the RIE apparatus easily corrode by beingexposed to plasma, so that a material having a high plasma resistance,such as yttrium oxide (yttria) and aluminum oxide (alumina), is coatedthereon as a protective film.

However, even when the protective film such as yttrium oxide is coatedon the inner wall and the internal structural members of the RIEapparatus, the protective film degrades due to shedding of particles,cracks, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating one example of a part mounted on aplasma processing apparatus in a first embodiment;

FIG. 2A is a tracing illustrating one example of an yttrium oxide filmin the first embodiment;

FIG. 2B is a photograph illustrating one example of the yttrium oxidefilm in the first embodiment;

FIG. 3A is a tracing further magnifying a part in FIG. 2A;

FIG. 3B is a photograph further magnifying a part in FIG. 2B;

FIG. 4 is a diagram illustrating film forming conditions of yttriumoxide films formed by an impact sintering method (Examples 1 to 7) and aconventional thermal spray method (Comparison Example 1);

FIG. 5 is a diagram illustrating an evaluation result of an yttriumoxide film formed under each condition shown in FIG. 4;

FIG. 6 is a diagram illustrating an evaluation result of the plasmaresistance;

FIG. 7 is a cross-sectional view schematically illustrating one exampleof a configuration of a plasma processing apparatus in a secondembodiment;

FIG. 8A is a plan view illustrating one example of a configuration of ashower head coated with a protective film in the second embodiment;

FIG. 8B is a schematic cross-sectional view of the shower head coatedwith the protective film in the second embodiment near a gas ejectionport formed region;

FIG. 9A and FIG. 9B are perspective views illustrating one example of aconfiguration of a deposition shield coated with the protective film inthe second embodiment;

FIG. 10A is a perspective view illustrating one example of aconfiguration of an insulator ring coated with the protective film inthe second embodiment;

FIG. 10B is a cross-sectional view illustrating one example of theconfiguration of the insulator ring coated with the protective film inthe second embodiment;

FIG. 11 is a diagram illustrating a degree of a particle shedding rateof the protective film in the second embodiment; and

FIG. 12 is a diagram illustrating a degree of an etching rate of theprotective film in the second embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a plasma processing apparatusthat includes a process target holding portion that holds a processtarget in a chamber and a plasma generating unit that turns gasintroduced into the chamber into plasma, and processes the processtarget by using generated plasma is provided. An yttrium oxide film isformed on an inner wall of the chamber and a surface of a structuralmember in the chamber on a generation region side of plasma generated inthe plasma generating unit. The yttrium oxide film includes yttriumoxide particles, has a film thickness of 10 μm or more and 200 μm orless, has a film density of 90% or more, and is such that yttrium oxideparticles, which are present in a unit area 20 μm×20 μm and whose grainboundary is confirmable, are 0 to 80% in area ratio and yttrium oxideparticles, whose grain boundary is not confirmable, is 20 to 100% inarea ratio.

A plasma processing apparatus according to the embodiments will beexplained in detail below with reference to the accompanying drawings.The present invention is not limited to these embodiments.

First Embodiment

A plasma processing apparatus in the first embodiment is an apparatus onwhich parts for the plasma processing apparatus, which include anyttrium oxide film formed by an impact sintering method, are mounted.The yttrium oxide film is an yttrium oxide film (hereinafter, an yttriumoxide film in a semi-molten state) that includes yttrium oxide particlesin which adjacent particles, at least the surfaces of which are in amolten state, are bonded and solidified and in which part of grainboundaries cannot be seen. This semi-molten-state yttrium oxide filmincludes yttrium oxide particles, has a film thickness of 10 μm or more,has a film density of 90% or more, and includes yttrium oxide particles,which are present in a unit area 20 μm×20 μm and whose grain boundarycan be confirmed, by 0 to 80% in area ratio and includes yttrium oxideparticles, whose grain boundary cannot be confirmed, by 20 to 100% inarea ratio.

FIG. 1 is a diagram illustrating one example of a part mounted on theplasma processing apparatus in the first embodiment. FIG. 1 illustratesa part 1 for the plasma processing apparatus, an yttrium oxide film 2,and a substrate 3. Yttrium oxide has resistance to plasma attack andradical attack (for example, active F radical) and therefore has noproblem, however, particularly, yttrium oxide having resistant tofluorine plasma is preferable.

Moreover, the purity of yttrium oxide particles is preferably 99.9% ormore. A large amount of impurities in yttrium oxide particles causescontamination in a manufacturing process of semiconductors. Therefore,yttrium oxide particles whose purity is 99.9% or more are preferablyused.

An yttrium oxide film includes yttrium oxide particles. For example, ifthe film is formed by a typical thermal spray method, the film is formedin a state where yttrium oxide particles are in a molten state.Therefore, the yttrium oxide particles are in flat shape. On thecontrary, in the first embodiment, because yttrium oxide particles arenot melted and thus do not have a flat shape, and the yttrium oxide filmincludes yttrium oxide particles, which are present in a unit area 20μm×20 μm and whose grain boundary can be identified, by 0 to 80% in arearatio and includes yttrium oxide particles, whose grain boundary cannotbe identified, by 20 to 100% in area ratio.

Yttrium oxide particles whose grain boundary can be confirmed can berecognized in a magnified photograph. For example, the yttrium oxideparticles can be recognized by taking a 5000-times-magnified photographby an electron microscope. FIG. 2A is a tracing illustrating one exampleof the yttrium oxide film in the first embodiment and FIG. 2B is aphotograph illustrating one example of the yttrium oxide film in thefirst embodiment. FIG. 3A is a tracing further magnifying a part in FIG.2A and FIG. 3B is a photograph further magnifying a part in FIG. 2B.FIG. 2A is a diagram tracing the photograph in FIG. 2B and FIG. 3A is adiagram tracing the photograph in FIG. 3B. These figures illustrateyttrium oxide particles 4 whose grain boundary cannot be confirmed andyttrium oxide particles 5 whose grain boundary can be confirmed.

“Yttrium oxide particles whose grain boundary can be confirmed” areparticles in which a grain boundary of each particle can be confirmed bya contrast difference in a magnified photograph. On the other hand,“yttrium oxide particles whose grain boundary cannot be confirmed” areparticles in which adjacent particles are bonded and a grain boundary ofeach particle cannot be confirmed in a magnified photograph. Moreover, aunit area is 20 μm×20 μm and an area of each of “yttrium oxide particleswhose grain boundary can be confirmed” and “yttrium oxide particleswhose grain boundary cannot be confirmed” in an arbitrary predeterminednumber (for example, three) of the unit areas selected in a sample ismeasured, and the average thereof is set as the area ratio of each of“yttrium oxide particles whose grain boundary can be confirmed” and“yttrium oxide particles whose grain boundary cannot be confirmed”. InFIG. 2A to FIG. 3B, both the particle group of the “yttrium oxideparticles 5 whose grain boundary can be confirmed” and the particlegroup of the “yttrium oxide particles 4 whose grain boundary cannot beconfirmed” exist in a mixed state.

The impact sintering method is a film forming method of forming a filmby spraying particles by combustion flame, and is a method of impactingparticles onto a substrate at high speed (for example, sound speed orfaster) and forming a film by sinter bonding the particles by crushingheat of the particles by the impact. Therefore, an yttrium oxide filmincluding yttrium oxide particles having a crushed shape rather than aparticle shape of raw powder tends to be formed. In the firstembodiment, in such the impact sintering method, a film is formed bycontrolling such that the spray rate of yttrium oxide particles isaccelerated in a state where the yttrium oxide particles are not meltedor only the surface layer thereof is melted to be equal to or fasterthan a critical speed at which the particles start to deposit. Anyttrium oxide particle whose surface layer is melted is bonded to anadjacent yttrium oxide particle by crushing heat when impacting onto thesubstrate, so that an yttrium oxide film including yttrium oxideparticles whose grain boundary cannot be confirmed is formed. At thistime, the entire yttrium oxide particle may be melted by crushing heatwhen the yttrium oxide particle impacts onto the substrate instead ofonly the surface layer. In this case also, a similar yttrium oxide filmis formed. An yttrium oxide particle whose surface layer is not meltedis melted in some cases at least in the surface layer thereof bycrushing heat when impacting onto the substrate, so that an yttriumoxide film including yttrium oxide particles in which the grain boundarybetween adjacent yttrium oxide particles cannot be confirmed is formed.In this manner, with the use of a high-speed spraying, raw powder is notsprayed in a molten state as in a thermal spraying, so that yttriumoxide particles can be deposited in a state of substantially maintaininga powder form of the yttrium oxide particles as raw powder. Therefore,stress in a film is not generated, so that a dense (high film density)yttrium oxide film having a high bonding force can be formed.

In this manner, the impact sintering method is capable of high-speedspraying, so that a structure in which “yttrium oxide particles whosegrain boundary can be confirmed” and “yttrium oxide particles whosegrain boundary cannot be confirmed” exist in a mixed state can be easilyobtained. When the sum of the area ratio of “yttrium oxide particleswhose grain boundary can be confirmed” and “yttrium oxide particleswhose grain boundary cannot be confirmed” is 100%, the area ratio of“yttrium oxide particles whose grain boundary can be confirmed” is 0 to80% and the area ratio of “yttrium oxide particles whose grain boundarycannot be confirmed” is 20 to 100%.

If the area ratio of “yttrium oxide particles whose grain boundary canbe confirmed” exceeds 80%, crushing heat by the impact is notsufficient, which causes a rapid cooling state in deposition, so thatthe density and the bonding force of a film decrease and a crack isgenerated in some cases. The area ratio of “yttrium oxide particleswhose grain boundary can be confirmed” is preferably 0 to 50%. This isequivalent to that the area ratio of “yttrium oxide particles whosegrain boundary cannot be confirmed” is preferably in a range of 50 to100%.

Moreover, the film thickness of the yttrium oxide film is desirably 10μm or more. If the film thickness is less than 10 μm, the effect ofproviding the yttrium oxide film is not sufficiently obtained and thismay cause film separation. The upper limit of the film thickness of theyttrium oxide film is not particularly limited, however, if the film istoo thick, no further effect can be obtained and moreover, a crack iseasily generated due to accumulation of internal stress and this becomesa factor of cost increase. Therefore, the thickness of the yttrium oxidefilm is 10 to 200 μm and is more preferably, 50 to 150 μm.

Moreover, the film density needs to be 90% or more. The film density isan antonym of the porosity, and the film density being 90% or more isthe same as the porosity being 10% or less. As a measuring method of thefilm density, an oxide film is cut in the film thickness direction, amagnified photograph (for example, 500 times) of its cross-sectionalstructure is taken by an optical microscope, and the area ratio of poresin the magnified photograph is calculated. Then, the film density iscalculated by “film density (%)=100−area ratio of pores”. In thecalculation of the film density, an area of a unit area 200 μm×200 μm isanalyzed. When the film thickness is thin, the film density is measuredat a plurality of locations until the total cross-sectional area becomesthe unit area 200 μm×200 μm.

The film density is preferably 90% or more, more preferably 95% or more,and still more preferably 99% or more and 100% or less. When a lot ofpores (voids) are present in the yttrium oxide film, corrosion, such asplasma attack, proceeds from the pores, which reduces the life of theoxide film. Specially, it is desirable that there are not many pores inthe surface of the yttrium oxide film.

Moreover, the surface roughness Ra of the yttrium oxide film ispreferably 3 μm or less. If the surface irregularity of the yttriumoxide film is large, plasma attack or the like is easy to concentrate,which may reduce the life of the film. The surface roughness Ra ismeasured according to JIS-B-0601-1994. Preferably, the surface roughnessRa is 2 μm or less.

Moreover, the average particle diameter of yttrium oxide particles whosegrain boundary can be confirmed is preferably 2 μm or less and theaverage particle diameter of all yttrium oxide particles includingyttrium oxide particles whose grain boundary cannot be confirmed ispreferably 5 μm or less.

As will be described later, yttrium oxide powder as raw powder used inthe impact sintering method preferably has an average particle diameterin a range of 1 to 5 μm. If the average particle diameter of yttriumoxide particles as raw powder exceeds 5 μm, when the particles impact,the particles are not crushed and scatter, so that a film is difficultto form and moreover, a film may be damaged by a blast action of theparticles themselves and a crack may be generated. On the other hand, ifthe average particle diameter of yttrium oxide particles becomes 5 μm orless, when fine particles impact, crushing proceeds moderately andparticle bonding is facilitated by heat generated by the crushing, sothat a film is easily formed. This formed film has a large bonding forcebetween particles, so that wear due to plasma attack and radical attackis reduced and particle generation is reduced, thereby improving theplasma resistance. A more preferred value of the particle diameter ofparticles is 1 μm or more and 3 μm or less, and if the particle diameterbecomes less than 1 μm, it becomes difficult to proceed crushing ofparticles, so that although a film is formed, the film becomes a lowdensity film and therefore the plasma resistance and the corrosionresistance decrease. Therefore, the range of application of the fineparticle diameter is preferably 1 to 5 μm. However, if fine particles ofless than 1 μm are less than 5% of all yttrium oxide particles, filmformation is not degraded, so that powder containing fine particles ofless than 1 μm may be used.

The average particle diameter is obtained by using a magnifiedphotograph as shown in FIG. 2B. The longest diagonal line in particlesin the photograph is set as the particle diameter of yttrium oxideparticles whose grain boundary can be confirmed. For yttrium oxideparticles whose grain boundary cannot be confirmed, a temporary circleof each particle is used and the diameter thereof is set as the particlediameter. This operation is performed for a predetermined number ofparticles for each particle group (for example, 50 particles, totally100 particles) and the average thereof is set as the average particlediameter.

When an X-ray diffraction analysis (X-ray diffraction Technique:hereinafter, XRD analysis) is performed on the yttrium oxide film, andthe resulting strongest peak of a cubical crystal (cubic) is Ic and theresulting strongest peak of a monoclinic crystal (monoclinic) is Im, theratio Im/Ic is preferably 0.2 to 0.6. The XRD analysis is performedunder the condition of a 2θ method, using a Cu as a target, setting atube voltage to 40 kV, and setting a tube current to 40 mA.

The strongest peak of a cubical crystal is detected between 28 and 30°.Moreover, the strongest peak of a monoclinic crystal is detected between30 and 33°. Normally, commercial yttrium oxide particles are a cubicalcrystal. Crystalline change occurs in some cases in part of the yttriumoxide particles by crushing heat in the impact sintering method,however, if crystalline change occurs in many yttrium oxide particles,the internal stress is generated and thus the film characteristicsdegrade. Therefore, Im/Ic is preferably in a range of 0.2 to 0.6.

Next, the manufacturing method of parts for a dry etching apparatus inthe first embodiment is explained. The manufacturing method of the partsfor the plasma processing apparatus, on which the yttrium oxide film isformed by the impact sintering method in the first embodiment, includesa process of supplying slurry containing yttrium oxide particles intocombustion flame and a process of spraying yttrium oxide particles ontoa substrate at a spray rate of 400 to 1000 m/sec. The average particlediameter of yttrium oxide particles is preferably 1 to 5 μm. Moreover,slurry containing yttrium oxide particles is preferably supplied to thecenter of combustion flame. The temperature of combustion flame at thistime is desirably 3000° C. or less.

The impact sintering method is a film forming method of supplying slurrycontaining yttrium oxide particles into combustion flame and sprayingyttrium oxide particles at high speed. A film forming apparatus thatperforms the impact sintering method includes a combustion source supplyport from which a combustion source is supplied and a combustion chamberconnected thereto. Combustion flame is generated in a combustion flameport by combusting the combustion source in the combustion chamber. Aslurry supply port is provided near combustion flame and yttrium oxideparticle slurry supplied from the slurry supply port is sprayed to thesubstrate from the combustion flame via a nozzle to form a film. Thecombustion source is oxygen, acetylene, heating oil, or the like and twoof them may be used for a combustion source if needed.

When forming an yttrium oxide film by the impact sintering method, thespray rate of yttrium oxide particles is preferably in a range of 400m/sec or more and 1000 m/sec or less. If the spray rate is low, crushingwhen particles impact becomes insufficient and a film having a high filmdensity may not be obtained. Moreover, if the spray rate exceeds 1000m/sec, the impact is too strong, so that the blast effect by yttriumoxide particles occurs and a desired film is difficult to obtain.

Moreover, when yttrium oxide particle slurry is supplied from the slurrysupply port, the slurry is preferably supplied to the center ofcombustion flame. If yttrium oxide particle slurry is supplied to theoutside of combustion flame, part of yttrium oxide particles is sprayedfrom the outside of the combustion flame and part thereof is sprayedafter reaching the center of the combustion flame, so that the sprayrate is not stabilized. Moreover, the temperature is slightly differentbetween the outside and the inside in the same combustion flame, so thatthe film quality becomes inconsistent. On the contrary, if yttrium oxideparticle slurry is supplied to the center of combustion flame, a film isformed at the same temperature and the same spray rate, so that the filmquality becomes consistent and thus it becomes possible to control thestructure of particles whose grain boundary can be confirmed andparticles whose grain boundary cannot be confirmed.

Moreover, the impact sintering method is a film forming method offorming a film by spraying particles by combustion flame and is a methodof forming a film by impacting particles at high speed and sinterbonding the particles by crushing heat of the particles by the impact.Therefore, an yttrium oxide film including yttrium oxide particleshaving a crushed shape rather than a particle shape of raw powder tendsto be formed. Moreover, an yttrium oxide film having a high film densitycan be obtained by controlling such that the spray rate of yttrium oxideparticles is accelerated in a state where the yttrium oxide particlesare not melted or only the surface layer thereof is melted to be equalto or faster than a critical speed at which the particles start todeposit. The impact sintering method is capable of high-speed spraying,so that “particles whose grain boundary cannot be confirmed” can beeasily obtained. Thus, it is possible to efficiently obtain the yttriumoxide film that includes yttrium oxide particles, whose grain boundarycan be confirmed, by 0 to 80% in area ratio and yttrium oxide particles,whose grain boundary cannot be confirmed, by 20 to 100% in area ratio asin the first embodiment.

Moreover, it is effective to adjust a spray distance L from the nozzleto the substrate in a control of “particles whose grain boundary can beconfirmed” and “particles whose grain boundary cannot be confirmed”. Asdescribed above, the impact sintering method is a method of sprayingyttrium oxide particles at high speed by using combustion flame andsinter bonding and depositing the yttrium oxide particles by utilizingcrushing heat of the particles at the time of the impact. In order toform a film without forming yttrium oxide particles, which are onceheated by combustion flame, into a melted flat shape, the spray distanceL is preferably 100 to 400 mm. The spray distance L of less than 100 mmis too close, so that oxide particles are not crushed and therefore afilm in which particles are sinter bonded is hard to obtain. On theother hand, the spray distance L exceeding 400 mm is too far, so thatthe impact force becomes low and therefore a target oxide film is hardto obtain. Melted and unmelted structures can be controlled bycontrolling the spray rate and the oxide particle size as raw powderdescribed above. Preferably, the spray distance L is 100 to 200 mm.

Moreover, yttrium oxide particle slurry is preferably slurry containingyttrium oxide particles having an average particle diameter of 1 to 5 μmas raw powder. Solvent to be slurried is preferably solvent that isrelatively easy to volatilize, such as methyl alcohol and ethyl alcohol.Yttrium oxide particles are preferably mixed with solvent after beingsufficiently crushed to be free from a coarse particle. For example,presence of a coarse particle of 20 μm or larger makes it difficult toobtain a uniform film. Moreover, yttrium oxide particles in slurry arepreferably 30 to 80 vol %. Slurry having a moderate flowability issmoothly supplied to a supply port and therefore the supply isstabilized, so that a uniform film can be obtained.

With the use of such an impact sintering method, an yttrium oxide filmcan be formed without changing a crystal structure of raw powder(yttrium oxide particle slurry). For example, yttrium oxide is a cubicalcrystal at room temperature. If yttrium oxide is exposed to hightemperature such as combustion flame in a thermal spray method, acrystal structure changes, however, yttrium oxide is not exposed to hightemperature in the impact sintering method, so that yttrium oxideparticles can form an yttrium oxide film while maintaining a stablecubical crystal.

The pars for the plasma processing apparatus as above can be applied tovarious plasma processing apparatuses. For example, micro-patterning ofvarious thin films, such as a dielectric film, an electrode film, and awiring film formed on an Si wafer or a substrate, can be performed byusing an RIE (Reactive Ion Etching) apparatus that performs a process byusing ions or radicals generated by turning halogen gas into plasma by aradio-frequency voltage applied between electrodes or an interactionbetween an electric field of microwaves and a magnetic field. The partsfor the plasma processing apparatus in the first embodiment can beapplied to any portion exposed to plasma. Therefore, they can be appliedto any part exposed to plasma, such as an inner wall part, without beinglimited to a wafer arrangement member. Moreover, the substrate on whichthe yttrium oxide film is formed is not limited to quartz and theyttrium oxide film may be provided on a metal member or a ceramicmember. Specially, although the technology can be applied to adeposition shield, an insulator ring, an upper electrode, a baffleplate, a focus ring, a shield ring, a bellows cover, and the likeexposed to plasma among parts used in the plasma processing apparatus,the technology is not limited to a field of a semiconductormanufacturing apparatus and can be applied also to parts of the plasmaprocessing apparatus such as a liquid crystal display device.

Moreover, the plasma resistance in the part for the plasma processingapparatus is improved significantly, so that particles can be reducedand the life of used parts can be prolonged. Therefore, according to theplasma processing apparatus using such parts for the plasma processingapparatus, particles during the plasma process can be reduced and thenumber of replacement times of the parts can be reduced.

Moreover, in an RIE apparatus utilizing high-density plasma, adielectric member is used in some cases to ensure insulation against aradio-frequency voltage applied for generating plasma. As a protectivefilm of a dielectric member exposed to plasma such as an upperelectrode, bi-layer coating, which is formed by depositing a highlyinsulating aluminum oxide film (alumite) and then forming the yttriumoxide film thereon, is effective. In terms of insulation, thicknessadjustment of an aluminum oxide film and formation of a high-densityfilm are important, and specially, when an aluminum oxide film having ana structure is densely formed, a further effect is exerted, so that itis preferable to set the condition equivalent to formation of theyttrium oxide film.

An aluminum oxide film is used as a lower layer, however, other oxidesor a mixture thereof may be used and it is preferable to select amaterial according to requisite characteristics. In the case of adouble-layered structure with an aluminum oxide film, the upper limitthereof is preferably 500 μm or less.

Moreover, because particles are sprayed at high speed by the impactsintering method and particles are deposited by its impact energy, whendepositing a film on a structural part, a blast treatment is not needed.Consequently, there is no residual blast member and generation of asurface defect, so that adhesion of a film improves. This is because afilm is formed directly on a part surface by causing a surface oxidefilm of a structural member to be destroyed by a high-speed impact ofparticles and exposing an active surface and a film is formed by causingbonding to occur between particles by heat generation due to particlebreakdown in the particle impact thereafter.

Therefore, generation of particles due to separation of attached mattersdeposited on the parts for the apparatus can be suppressed and thenumber of times of cleaning the apparatus and replacing the parts can besignificantly reduced. Reduction of particle generation contributeslargely to reduce defects at the time of an etching process and defectsin a film at the time of various thin film formation in semiconductormanufacturing and moreover, to improvement in yield of parts andelements obtained by using it. Moreover, reduction in the number oftimes of cleaning the apparatus and replacing the parts and prolongationof the useful life of the parts contribute largely to improvement inproductivity and reduction in running costs.

The first embodiment is explained in detail below with reference toexamples.

FIG. 4 is a diagram illustrating film forming conditions of yttriumoxide films formed by the impact sintering method (Examples 1 to 7) anda conventional thermal spray method (Comparison Example 1). An yttriumoxide film is formed on an aluminum substrate (100 mm×200 mm) under theconditions shown in FIG. 4 by the impact sintering method using acombustion-flame type spraying apparatus to be the part for the plasmaprocessing apparatus. In each example, ethyl alcohol is used as solventof yttrium oxide particle slurry. Moreover, in each example, high-purityoxide particles with the purity of 99.9% or more are used as raw powderto be used. Furthermore, yttrium oxide (Y₂O₃) particles as raw powderare a cubic crystal, and yttrium oxide particles free from a coarseparticle exceeding 20 μm by sufficient crushing and screening are used.Moreover, in Comparison Example 1, an yttrium oxide film is formed by aplasma thermal spray method.

FIG. 5 is a diagram illustrating an evaluation result of an yttriumoxide film formed under each condition shown in FIG. 4. For the yttriumoxide films in each example and the comparison example shown in FIG. 4,the film density, the area ratio of particles whose grain boundary canbe confirmed and particles whose grain boundary cannot be confirmed, andthe average particle diameter of particles whose grain boundary can beconfirmed in an yttrium oxide film are measured and the crystalstructure is analyzed by the XRD method.

In terms of the film density, a magnified photograph (500 times) istaken so that the total unit area in the film cross section becomes 200μm×200 μm and the film density is obtained from a ratio of pores in thephotograph. In terms of the area ratio of particles whose grain boundarycan be confirmed and particles whose grain boundary cannot be confirmed,a magnified photograph (5000 times) of a unit area 20 μm×20 μm in thefilm surface is taken and the area ratio is obtained under the conditionthat particles in which a grain boundary of one yttrium oxide particleis confirmed are determined as “particles whose grain boundary can beconfirmed” and particles in which grain boundaries are bonded and cannotbe confirmed are determined as “particles whose grain boundary cannot beconfirmed”. This operation is performed at arbitrary three locations andthe average thereof is determined as the area ratio (%) of “particleswhose grain boundary can be confirmed” and “particles whose grainboundary cannot be confirmed”. Moreover, the average particle diameterof “particles whose grain boundary can be confirmed” is obtained byusing the same magnified photograph. Furthermore, the crystal structureis examined by the ratio Im/Ic of the strongest peak Ic of a cubiccrystal and the strongest peak Im of a monoclinic crystal detected inthe XRD analysis (using a Cu target, setting a tube voltage to 40 kV,and setting a tube current to 40 mA).

As is apparent from FIG. 5, in the yttrium oxide films according to thepresent examples, the film density is high and the ratio (area ratio) of“yttrium oxide particles whose grain boundary can be confirmed” is in arange of 0 to 80%. Moreover, with the use of the impact sinteringmethod, the average particle diameter of “yttrium oxide particles whosegrain boundary can be confirmed” is slightly smaller than the size(about 5 μm) of raw powder. Furthermore, because the particles are notmelted more than necessary, the crystal structure is partially the sameas raw powder (Im/Ic=0.2 to 0.6).

Moreover, although not shown in FIG. 5, the yttrium oxide films inExamples 1 to 6 have a surface roughness Ra of 3 μm or less. The surfaceroughness Ra of the yttrium oxide film in Example 7 is as large as 6.2μm, and this is considered to be because the number of “particles whosegrain boundary cannot be confirmed” is small and thus the surfaceirregularity becomes large. Furthermore, in Comparison Example 1, thesurface roughness Ra of the yttrium oxide film is 3.4 μm.

Next, FIG. 6 is a diagram illustrating an evaluation result of theplasma resistance. Each yttrium oxide film in each example and thecomparison example shown in FIG. 4 is arranged in the plasma processingapparatus and is exposed to plasma generated by a mixed gas of CF₄ (80sccm)+0 ₂ (20 sccm)+Ar (100 sccm). The pressure in an RIE chamber is setto 20 mTorr and the RF output is set to 100 W, and after continuouslyoperating for 12 hours (“30 minutes discharging→10 minutes cooling”×24times), an amount of shed particles of the yttrium oxide film isexamined by a peeling evaluation by a Scotch tape method. Specifically,after attaching Scotch tape to the yttrium oxide film, the tape ispeeled, the tape is subjected to SEM (Scanning Electron Microscope)observation, and an area, in which shed particles are adhered, presentin a field of view of 80 μm×60 μm is measured. Moreover, the weight of amember on which the yttrium oxide film is formed is measured by aprecision balance before and after performing the above test and theweight loss is obtained.

FIG. 6 shows that, in the impact sintering method (Examples 1 to 7), theweight loss is smaller than the conventional thermal spray method(Comparison Example 1) and an amount of shed particles from the yttriumoxide film is also smaller by one or more orders of magnitude.Consequently, it is found that the parts for the RIE apparatus, on whichthe protective film is formed by the impact sintering method accordingto the present examples, are resistant to plasma attack and radicalattack. Being resistant to plasma attack and radical attack means thatgeneration of particles when using the RIE apparatus can be efficientlysuppressed.

In each of the above examples, the yttrium oxide film by the impactsintering method is directly formed on the surface of each part as anexample, however, an effect of improving also insulation as the partscan be exerted by forming at least one layer of a dielectric film, suchas an aluminum oxide film, between a part surface and the yttrium oxidefilm and forming the yttrium oxide film by the impact sintering methodon the outermost surface thereof.

As explained above, according to the parts for the RIE apparatus in thefirst embodiment, corrosion of a film due to radicals of corrosive gascan be suppressed, so that stability of each part and the film itselfcan be improved, enabling to suppress generation of particles from theparts or the film. Furthermore, because the life of used parts isprolonged and products generated by corrosion can be reduced, the numberof times of cleaning the apparatus and replacing the parts can bereduced.

Second Embodiment

In the second embodiment, a specific example of applying the yttriumoxide film explained in the first embodiment to structural members of aplasma processing apparatus is explained.

FIG. 7 is a cross-sectional view schematically illustrating one exampleof the configuration of the plasma processing apparatus in the secondembodiment. In this embodiment, as a plasma processing apparatus 10, anRIE apparatus is exemplified. The plasma processing apparatus 10includes, for example, a sealed aluminum chamber 11. This chamber 11 isgrounded.

A support table 21, which horizontally supports a wafer 100 as a processtarget and functions as a lower electrode, is provided in the chamber11. On the surface of the support table 21, a not-shown holdingmechanism, such as an electrostatic chuck mechanism thatelectrostatically adsorbs the wafer 100, is provided. An insulator ring22 is arranged to cover the side surface and the peripheral portion ofthe bottom surface of the support table 21, and a focus ring 23 isprovided on the outer periphery of the support table 21 above theportion covered by the insulator ring 22. This focus ring 23 is a memberthat adjusts an electric field so that the electric field is not biasedwith respect to a vertical direction (direction vertical to the wafersurface) in the peripheral portion of the wafer 100 when etching thewafer 100.

Moreover, the support table 21 is supported on a support portion 12,which projects vertically upward in a tubular shape from the bottom wallnear the center of the chamber 11, via the insulator ring 22 to bepositioned near the center in the chamber 11. A baffle plate 24 isprovided between the insulator ring 22 and the side wall of the chamber11. The baffle plate 24 includes a plurality of gas exhaust holes 25penetrating in the thickness direction of the plate. Moreover, a feeder31, which supplies radio-frequency power, is connected to the supporttable 21 and a blocking capacitor 32, a matching box 33, and aradio-frequency power source 34 are connected to this feeder 31.Radio-frequency power of a predetermined frequency is supplied from theradio-frequency power source 34 to the support table 21.

A shower head 41, which functions as an upper electrode, is providedabove the support table 21 to face the support table 21 functioning as alower electrode. The shower head 41 is fixed to the sidewall near theupper portion of the chamber 11 at a predetermined distance from thesupport table 21 to face the support table 21 in parallel therewith.With such a structure, the shower head 41 and the support table 21configure a pair of parallel plate electrodes. Moreover, a plurality ofgas ejection ports 42 penetrating in the thickness direction of theplate is provided in the shower head 41.

A gas supply port 13, from which process gas used in the plasma processis supplied, is provided near the upper portion of the chamber 11 and anot-shown gas supplying apparatus is connected to the gas supply port 13via a pipe.

A gas exhaust port 14 is provided in the lower portion of the chamber 11lower than the support table 21 and the baffle plate 24 and a vacuumpump as a not-shown exhausting unit is connected to the gas exhaust port14 via a pipe.

Moreover, a deposition shield 45, which prevents adhesion of depositiongenerated in the plasma process to the sidewall of the chamber 11, isprovided on the sidewall of the chamber 11 in a region partitionedbetween the baffle plate 24 and the shower head 41. Moreover, an opening15 for moving the wafer 100 into and out of the chamber 11 is formed inthe sidewall at a predetermined position of the chamber 11 and a shutter46 is provided at the portion of the deposition shield 45 correspondingto this opening 15. The shutter 46 has a role of partitioning betweenthe outside and the inside of the chamber 11, and when moving the wafer100 into and out of the chamber 11, the shutter 46 is opened to connectthe opening 15 and the inside of the chamber 11.

The region partitioned by the support table 21, the baffle plate 24, andthe shower head 41 in the chamber 11 becomes a plasma processing chamber61, the upper region in the chamber 11 partitioned by the shower head 41becomes a gas supply chamber 62, and the lower region in the chamber 11partitioned by the support table 21 and the baffle plate 24 becomes agas exhaust chamber 63.

A summary of a process in the plasma processing apparatus 10 configuredas above is explained. First, the wafer 100 as a process target isplaced on the support table 21 and is fixed, for example, by anelectrostatic chuck mechanism. Next, the inside of the chamber 11 isevacuated by a not-shown vacuum pump connected to the gas exhaust port14. At this time, the gas exhaust chamber 63 and the plasma processingchamber 61 are connected through the gas exhaust holes 25 provided inthe baffle plate 24, so that the inside of the whole chamber 11 isevacuated by the vacuum pump connected to the gas exhaust port 14.

Thereafter, when the inside of the chamber 11 reaches a predeterminedpressure, because the plasma processing chamber 61 and the gas supplychamber 62 are connected through the gas ejection ports 42 of the showerhead 41, process gas is supplied to the gas supply chamber 62 from thenot-shown gas supplying apparatus and is supplied to the plasmaprocessing chamber 61 via the gas ejection ports 42 of the shower head41. When the pressure inside the plasma processing chamber 61 reaches apredetermined pressure, in a state where the shower head 41 (upperelectrode) is grounded, a radio-frequency voltage is applied to thesupport table 21 (lower electrode) to generate plasma in the plasmaprocessing chamber 61. Because a radio-frequency voltage is applied tothe lower electrode, a potential gradient is formed between plasma and awafer, so that ions in plasma gas are accelerated toward the supporttable 21, whereby an etching process is performed.

As described above, a surface of a structural member on a side incontact with a plasma generation region, that is, the surface of thestructural member of the plasma processing chamber 61 is exposed toplasma and easily degraded, so that a protective film 50 is formed.Specifically, the protective film 50 including the yttrium oxide film ina semi-molten state explained in the first embodiment is formed on thesurface of the support table 21 on the side on which the wafer 100 isplaced, the surface of the insulator ring 22, the surface of the focusring 23, the surface of the baffle plate 24 on the plasma processingchamber 61 side, the surface of the shower head 41 on the plasmaprocessing chamber 61 side, the surface of the deposition shield 45 onthe plasma processing chamber 61 side, and the surface of the shutter 46on the plasma processing chamber 61 side.

FIG. 8A and FIG. 8B are diagrams illustrating one example of theconfiguration of the shower head coated with the protective film in thesecond embodiment, in which FIG. 8A is a plan view and FIG. 8B is aschematic cross-sectional view near a gas ejection port formed region.In this example, the shower head 41 as a gas supplying member has a diskshape and the gas ejection ports 42, which penetrate through theplate-shaped member in the thickness direction, are provided in apredetermined range from the center of the shower head 41. The entiresurface of one main surface of the shower head 41, that is, the surfaceon the side exposed to plasma during the plasma process in the plasmaprocessing apparatus 10 is coated with the protective film 50.

The gas ejection port 42 typically has a diameter of about a few hundredμm to a few mm and has a complex cross-sectional shape in a longitudinaldirection of the hole so that process gas can be supplied uniformly andstably in the chamber 11. Therefore, if the protective film 50 is formednear the gas ejection ports 42, stress is concentrated in a portionhaving a large curvature, so that a crack is easily generated. Moreover,the shower head 41 also functions as an upper electrode, and when thegas ejection ports 42 are provided in such an electrode, an electricfield is concentrated in a portion having a large curvature, so that aparticularly-high plasma resistance is required.

Thus, the surface of the shower head 41 including the gas ejection ports42 is coated with the protective film 50 formed of the yttrium oxidefilm formed by the impact sintering method shown in the firstembodiment, so that the protective film 50, which has improved plasmaresistance and is not easily peeled off, can be obtained on the surfaceof the shower head 41. Moreover, as explained in the first embodiment,the area ratio of yttrium oxide particles whose grain boundary cannot beconfirmed is set to 20 to 100% and the area ratio of yttrium oxideparticles whose grain boundary can be confirmed is set to 80 to 0%, sothat adjacent particles are bonded together, enabling to obtain thedense protective film 50 in which particles do not shed easily.

The forming method of the protective film 50 onto the surface of theshower head 41 is similar to the forming method of the protective film50 by the impact sintering method explained in the first embodiment, andthe protective film 50 is formed on the shower head 41 as a processingtarget with the thickness of 10 to 200 μm. The gas ejection port 42includes a first hole 421, which penetrates through the plate-likeshower head 41 in its thickness direction with a predetermined diameter,and a second hole 422 whose opening diameter gradually increases towardthe plasma processing chamber 61 side from the first hole 421, and theprotective film 50 is formed from the surface (main surface) of theshower head 41 on the side facing the plasma processing chamber 61 tothe inner wall of the second holes 422. However, the first holes 421 areapproximately vertical to the formation surface of the gas ejectionports 42 of the shower head 41, so that substantially no protective film50 is formed on the inner wall of the first holes 421. Moreover, thethickness of the protective film 50 formed on the surface of the secondhole 422 gradually increases in a direction in which the openingdiameter increases from near the boundary with the first hole 421 andbecomes substantially a uniform thickness in a region in which the gasejection port 42 is not formed.

FIG. 9A and FIG. 9B are perspective views illustrating one example ofthe configuration of the deposition shield coated with the protectivefilm in the second embodiment. As shown in FIG. 9A, the depositionshield 45 as an inner wall protective member has a cylindrical shape tofit in the inner wall of the plasma processing chamber 61 portion of thechamber 11. A support member 451 fixable to the sidewall of the chamber11 is provided on one end portion of the cylindrical member in a heightdirection. Moreover, an opening 452 is provided also in the depositionshield 45 to match the formation position of the opening 15 of thechamber 11. As shown in FIG. 9B, the shutter 46 is provided to fit inthe opening 452. In this embodiment, the shutter 46 is configured to beslidable in the height direction of the cylindrical member. Theprotective film 50 is provided on the inner side surface of thedeposition shield 45 including the shutter 46.

In this manner, the etching resistance of the deposition shield 45improves by forming the protective film 50 on the deposition shield 45,so that the frequency of replacement of the deposition shield 45 can bereduced.

FIG. 10A and FIG. 10B are diagrams illustrating one example of theconfiguration of the insulator ring coated with the protective film inthe second embodiment, in which FIG. 10A is a perspective view and FIG.10B is a cross-sectional view. As shown in FIG. 10A and FIG. 10B, theinsulator ring 22 is, for example, formed of quartz (SiO₂) having acircular ring shape. The insulator ring 22 includes a lower cutoutportion 221, which is provided on the lower side to cover the outerperiphery of the support table 21 and to be fixed at a step portionprovided on the outer periphery of the support table 21, and an uppercutout portion 222 provided on the upper side to fix the focus ring 23.The protective film 50 is formed from an upper surface portion 223 to aside surface portion 224 excluding the upper cutout portion 222. Forexample, the protective film 50 can be provided from the upper surfaceportion 223 to the side surface portion 224 with a uniform thickness.

In FIG. 8A to FIG. 10B, the shower head 41, the deposition shield 45,and the insulator ring 22 are exemplified, however, the protective film50 can be formed by the impact sintering method in the similar manneralso on a portion exposed to plasma during the plasma process amongstructural members of the plasma processing apparatus.

FIG. 11 is a diagram illustrating the degree of the particle sheddingrate of the protective film in the second embodiment. In thisembodiment, after attaching Scotch tape to the protective film 50, thetape is peeled, the tape is subjected to SEM observation and an area ofyttrium oxide particles forming the protective film 50 present in afield of view of 80 μm×60 μm is measured, and the particle area per unitarea remained on the peeled side is obtained as the particle sheddingrate. In this embodiment, measurement is performed on an yttrium oxidefilm A formed by the method in the first embodiment and an yttrium oxidefilm B formed by a thermal spray method. Consequently, whereas theparticle shedding rate of the yttrium oxide film B formed by a thermalspray method as a typical method of forming an yttrium oxide film is1.664%, the particle shedding rate of the yttrium oxide film A is0.033%. That is, in the protective film 50 that uses the yttrium oxidefilm A in the present embodiment, adhesion to a film formation target iseffectively improved compared with a thermally sprayed film.

FIG. 12 is a diagram illustrating the degree of the etching rate of theprotective film in the second embodiment. Structural members on whichthe yttrium oxide films A and B are formed are arranged in an RIEapparatus, etching is performed for a predetermined time, andthereafter, an etching degree (for example, weight loss) is measured,thereby obtaining the etching rate of the protective film 50. In thisembodiment, the etching rate with reference to the yttrium oxide film Bis shown. As shown in this figure, it is found that in the protectivefilm 50 in which the yttrium oxide film A in the present embodiment isused, the etching rate is low compared with the yttrium oxide film Bformed by using a conventional thermal spray method, so that the etchingresistance is improved.

As above, according to the second embodiment, adhesion and the etchingresistance can be improved compared with a protective film by aconventional thermal spray method by applying the protective film 50including yttrium oxide particles formed by the impact sintering methodto structural members of the plasma processing apparatus. Consequently,the life of the structural members of the plasma processing apparatuscan be prolonged, so that the effect of lowering the manufacturing costof semiconductor devices manufactured by the plasma processing apparatusis obtained.

Moreover, an RIE apparatus is exemplified as the plasma processingapparatus in the above, however, it is not limited thereto and theprotective film 50 in the above embodiments can be applied to anyapparatus that performs a process by generating plasma or radicals, suchas a plasma enhanced CVD (Chemical Vapor Deposition) apparatus.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A plasma processing apparatus that includes a process target holdingportion that holds a process target in a chamber and a plasma generatingunit that turns gas introduced into the chamber into plasma, andprocesses the process target by using generated plasma, wherein anyttrium oxide film is formed on an inner wall of the chamber and asurface of a structural member in the chamber on a generation regionside of plasma generated in the plasma generating unit, and the yttriumoxide film includes yttrium oxide particles, has a film thickness of 10μm or more and 200 μm or less, has a film density of 90% or more, and issuch that yttrium oxide particles, which are present in a unit area 20μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in arearatio and yttrium oxide particles, whose grain boundary is notconfirmable, is 20 to 100% in area ratio.
 2. The plasma processingapparatus according to claim 1, wherein the plasma generating unit is aplate-like gas supplying member that is arranged to face the processtarget holding portion, supplies the gas to a side of the process targetholding portion via a gas ejection port, and functions as an electrodethat turns the gas into plasma.
 3. The plasma processing apparatusaccording to claim 2, wherein the gas supplying member includes a gasejection port that includes a first hole having a first diameter and asecond hole, which is connected to one end portion of the first hole,whose opening diameter increases from the end portion to be a seconddiameter larger than the first diameter, and which is provided on onemain surface side of the gas supplying member, and the yttrium oxidefilm is provided on a surface forming the second hole and the one mainsurface of the gas supplying member.
 4. The plasma processing apparatusaccording to claim 1, further comprising a tubular inner wall protectivemember provided to be fitted in an inner wall of the chamber exposed tothe plasma generation region, wherein the yttrium oxide film is formedon a surface of the inner wall protective member on the plasmageneration region side.
 5. The plasma processing apparatus according toclaim 4, wherein the inner wall protective member includes a shutterthat openably covers an opening provided to move the process targetbetween an inside and an outside of the chamber, and the yttrium oxidefilm is formed also on a surface of the shutter on the plasma generationregion side.
 6. The plasma processing apparatus according to claim 1,wherein the process target holding portion includes a support memberthat holds the process target and functions as an electrode that turnsthe gas into plasma, and an insulator ring that is provided to cover aside surface of the support member and is formed of a dielectricmaterial, and the yttrium oxide film is provided on an upper surface andan outer peripheral portion of the insulator ring to be the plasmageneration region side.
 7. The plasma processing apparatus according toclaim 6, wherein the process target holding portion includes a focusring that is arranged around the process target placed on the supportmember and is formed of a conductive material, and the yttrium oxidefilm is provided on a surface of the focus ring on the plasma generationregion side.
 8. The plasma processing apparatus according to claim 1,further comprising a baffle plate that connects an outer periphery ofthe process target holding portion and a sidewall of the chamber, andincludes a gas exhaust hole from which gas on the plasma generationregion side is exhausted, wherein the yttrium oxide film is provided ona surface of the baffle plate on the plasma generation region side. 9.The plasma processing apparatus according to claim 1, wherein theyttrium oxide particles are yttrium oxide particles whose purity is99.9% or more.
 10. The plasma processing apparatus according to claim 1,wherein the yttrium oxide film has a film thickness of 10 to 200 μm anda film density of 99% or more and 100% or less.
 11. The plasmaprocessing apparatus according to claim 1, wherein the yttrium oxideparticles whose grain boundary is confirmable have an average particlediameter of 2 μm or less.
 12. The plasma processing apparatus accordingto claim 1, wherein an average particle diameter of the yttrium oxideparticles is 5 μm or less.
 13. The plasma processing apparatus accordingto claim 1, wherein, when an XRD analysis is performed on the yttriumoxide film, a ratio Im/Ic is 0.2 to 0.6, where Ic is a strongest peak ofa cubic crystal and Im is a strongest peak of a monoclinic crystal. 14.The plasma processing apparatus according to claim 1, wherein a surfaceroughness Ra of the yttrium oxide film is 3 μm or less.
 15. The plasmaprocessing apparatus according to claim 1, wherein the yttrium oxidefilm is formed on an inner wall of the chamber and a surface of astructural member in the chamber via an aluminum oxide film.
 16. Theplasma processing apparatus according to claim 15, wherein the aluminumoxide film has an a structure.